[PATCH] netfilter: ipset: Fix overflow before widen in the bitmap_ip_create() function.

[Gavrilov Ilia]

When first_ip is 0, last_ip is 0xFFFFFFF, and netmask is 31, the value of
an arithmetic expression 2 << (netmask - mask_bits - 1) is subject
to overflow due to a failure casting operands to a larger data type
before performing the arithmetic.

Note that it's harmless since the value will be checked at the next step.

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: b9fed748185a ("netfilter: ipset: Check and reject crazy /0 input parameters")
Signed-off-by: Ilia.Gavrilov <Ilia.Gavrilov@xxxxxxxxxxx>
---
 net/netfilter/ipset/ip_set_bitmap_ip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/ipset/ip_set_bitmap_ip.c b/net/netfilter/ipset/ip_set_bitmap_ip.c
index a8ce04a4bb72..b8f0fb37378f 100644
--- a/net/netfilter/ipset/ip_set_bitmap_ip.c
+++ b/net/netfilter/ipset/ip_set_bitmap_ip.c
@@ -309,7 +309,7 @@ bitmap_ip_create(struct net *net, struct ip_set *set, struct nlattr *tb[],
 
 		pr_debug("mask_bits %u, netmask %u\n", mask_bits, netmask);
 		hosts = 2 << (32 - netmask - 1);
-		elements = 2 << (netmask - mask_bits - 1);
+		elements = 2UL << (netmask - mask_bits - 1);
 	}
 	if (elements > IPSET_BITMAP_MAX_RANGE + 1)
 		return -IPSET_ERR_BITMAP_RANGE_SIZE;
-- 
2.30.2